The human heart is a very complex organ that relies on both mechanical and electrical operation in order to perform properly. As with any complex mechanism, problems can and often do arise, with the heart. For example, over time the electrical pathways in the heart (which sequentially cause the atria and ventricles to contract) may fail, thereby causing the heart to lose its rhythm, which is known as arrhythmia. In that event, the ventricles will contract at improper times, and as a result the output of blood decreases. In addition, in some failing hearts the muscle of the heart no longer contracts the ventricles to a sufficient extent. Insufficient ventricular contraction can produce a dangerous reduction in the amount of blood flow.
Numerous attempts have been made to assist these diseased or failing hearts by applying external pressure directly to the heart. One such example is direct manual compression of the heart by a person's hand during open chest cardiopulmonary resuscitation. Often, however, the patient requires cardiac or circulatory support or assist for extended periods of time, such as hours, days, weeks, or for the rest of the patient's life. Thus, manual manipulation of the heart is not a solution to the problem in most cases.
Mechanical devices have been developed to apply external pressure directly to the heart. Some of these devices utilize an inflatable liner that surrounds the heart. For example, U.S. Pat. No. 5,119,804 Anstadt discloses a cup that is provided with an elastomeric liner. The heart is held in place within the liner, which is cyclically inflated and deflated to apply external pressure to the heart. While this device provides an improvement in hemodynamics for a diseased or failing heart, the device is not fully implantable. U.S. Pat. No. 5,131,905 Grooters and U.S. Pat. No. 6,238,334 Easterbrook, III et al. are further examples of external (as opposed to implantable) cardiac assist devices.
U.S. Pat. No. 6,464,655 Shahinpoor, at FIG. 6d and FIG. 7, illustrates an embodiment of the “Electrically-Controllable Multi-Fingered Resilient Heart Compression Device” disclosed therein. In the embodiment shown artificial muscles, specifically electro-active polymers, are used to create “soft fingers” that can be directly electrically powered and computer controlled by wires. See eg., U.S. Pat. No. 6,464,655 at column 8, lines 19–38, : The teachings of Shahinpoor are specifically incorporated by reference herein.
Another shortcoming inherent in the prior art devices results from the fact that relatively high pressures are applied almost exclusively to the central portion of the ventricles' outer surfaces. This causes the heart to deform into an unnatural, generally hourglass, shape and may even eventually cause trauma (e.g., bruises) to the heart, especially if one of the prior art devices is operated for an extended period of time.
It is an object of the present invention to provide a device which does not interfere with the normal contraction pattern or rhythm of the heart as long as the “normal” pattern provides sufficient cardiac output of blood (e.g., from about 1.5 to about 3 liters per minute) to sustain and support the activities in which the patient wishes to engage. However when normal cardiac output is insufficient to sustain day-to-day activities the present device provides cardiac assist by increasing blood flow by compressing the heart mechanically or hydraulically from the apex or tip of the heart to its base (or top) without abnormal compression of generally the middle portion of the heart.
It also is one aspect of the present invention to provide a generally cone-shaped, fully-implantable cardiac cuff, or cup, or incompressible or supporting envelope for efficiently assisting the mechanical compression of the heart. It is another aspect to operate such a cardiac cup without unduly deforming the natural shape of the heart during the mechanical or hydraulic compression of the heart.
It is a further object of the present invention to provide a fully implantable cardiac cup for assisting heart function, which applies substantially uniform fluid pressure against the exterior surface of at least a portion of the ventricular portion of the heart during the systolic phase.
It is yet a further object of the present invention to provide a cardiac cup for assisting a heart function that can be installed in its operative position with minimal movement of the heart. Generally speaking the device will be sutured or otherwise attached to the heart so as to prevent device migration during use.
It is another object of this invention to provide a fully-implantable pressure vessel and pacing device.